The human brain and spinal cord are protected, preserved and enveloped by a meningeal system comprising meningeal membranes. A meningeal membrane is composed of an intricate network of three overlapping tissue layers: the dura mater (or dura) outermost layer, the arachnoid middle layer, and the pia mater innermost layer. The outermost layer is tough and waterproof. The innermost layer follows along and contacts the entire surface of the brain and spinal cord, carrying blood vessels to service them. The middle layer acts as a gliding system between the inner and outer surfaces. Any damage to this network causes acute problems to the central nervous system.
Repairing damaged meningeal membranes has largely focused on implantable and/or resorbable constructs known as dural substitutes. These dural substitutes are grafted to the damaged dura mater and are designed to replace and/or regenerate the damaged tissue. A number of synthetic and animal based dural repair products are currently available. However, most of these are categorized into either suturable or onlay (sutureless) grafts, typically available in sponges, sheets, nonwoven matrixes or combinations thereof. In some instances, these products can be difficult to apply, and in some cases limited pliability, or moldability, may not enable them to adequately reach the entire damaged area.
Synthetic gelatin and polymeric dural sealants have also been disclosed. However, with these synthetic sealants, certain problems persist as well. Some are porous, therefore not creating a tight seal. They may also be nonelastic and/or insoluble, thus leading to time consuming application. Furthermore, most are subject to swelling once applied and/or implanted because they must be hydrated or mixed at the surgical site rather than being prepared in advance of the procedure. Swelling of the material, post implantation, can be detrimental to the patient, for example, where such swelling causes compression of brain tissue, a nerve root or the spinal cord.
Thus, there is a need for a dural graft material that is especially adapted for use in those areas or locations where it is difficult to apply conventional dural grafts. Furthermore, there is a need for a dural graft material which minimizes or eliminates post implantation swelling as well as reduces the quantity of implant material necessary to repair the damage. Finally, a dural graft material is needed which simplifies the procedure in terms of mateability, risks and time duration as compared with conventional dural graft products.